For a marine diesel engine application, a fluid-film journalbearing has a shaft diameter of 32 mm and the length of the bearingis 24 mm. The bearing uses SAE grade 20 oil as lubricant andoperates under a radial load. The inlet and outlet temperatures ofoil are 50oC and 110oC respectively. It is assumed that because ofthe shearing action there is a uniformly distributed energy releasein the lubricant that heats the lubricant film. During run-inoperation, the film temperature can be approximated as the averageof the inlet and outlet temperatures. Assuming reasonable designdata, perform an overall design assessment for the following fourcases:
Case 1: Applied load: 2.5 kN, Radial clearance: 0.04 mm, Shaftspeed: 1800 rpm
Case 2: Applied load: 5.0 kN, Radial clearance: 0.04 mm, Shaftspeed: 1800 rpm
Case 3: Applied load: 2.5 kN, Radial clearance: 0.04 mm, Shaftspeed: 3600 rpm
Case 4: Applied load: 2.5 kN, Radial clearance: 0.02 mm, Shaftspeed: 1800 rpm
a) Analyze and estimate the bearing design parameters such as,minimum film thickness, power loss, side flow, total flow andmaximum film pressure for the above four cases.
b) Which parameter is most influential for economical running ofthe bearing ? Justify with reasons.
c) Which parameter is most influential for safe running of thebearing ? Justify with reasons.
d) Compare and discuss the results for the above four cases.
